Household fireplaces have long been criticised as subject to numerous shortcomings, prominent among which are the difficulty of cleaning and keeping them clean of accumulated ashes and their notorious inefficiency in useful delivery of the heat of burning logs. Both of these defects are attributable to the conventional types of grate which necessarily include front cross bars providing upstanding abutments for holding the burning logs against rolling forward, and which include no means operating otherwise than by radiation for transmitting heat to the room space to be warmed. The frontal construction quite completely inhibits removal of ashes forwardly from the hearth while the grate remains in place, and reliance solely on radiation leaves the great bulk of the generated heat wasted by convection up the chimney.
Attempts at improving grate design to provide for proper log holding and at the same time facilitate easy ash removal have not been successful. Other efforts directed to conduction of heat to air in heat exchange tubes and convection therefrom into the room to be warmed have been equally unproductive, in most instances creating more problems than they solved, as by requiring frequent whole grate replacement because of early failure resulting from the burning out of such integral fixed components as air tubes, necessarily made of sheet metal thin enough for good conduction and thick enough to support burning logs of considerable weight.